Software complexity crisis brings huge obstacle to further progress in IT industry. To alleviate this problem, researchers are asked to build systems which can benefit from automation. With autonomic behavior, the real-time reactive systems can be more self-managed and adaptive to their environment. However, most of current formal approaches fail to specify such kind of system. In this paper, we proposed an approach to formally specify reactive autonomic systems. First, we used category theory to formalize reactive autonomic systems;then we focused on the categorization of self-configurations and work flows of reactive autonomic systems, and finally we used XML to specify the categorical models. In doing so, it can help to build the foundation of reactive autonomic systems with autonomic features and verify emergent behaviors.